At every stage of life the regulation of cerebral vascular tone and blood flow (CBF) is of vital importance. Many newborn infants, particularly those that are premature, have serious problems in the regulation of blood flow to their brains. This dysregulation may have serious consequences with intraventricular and germinal matrix hemorrhage with long-term neurological sequelae. The present studies seek to understand whereby maturational development alters fundamental signal transduction mechanisms in the cerebrovasculature of the fetus/premature newborn and the adult. This project is broadly based, multidisciplinary, and vertically integrated using physiologic, cellular, biochemical, and molecular approaches. Based on several decades of research findings, we shall test the overall hypothesis that maturational development is associated with significant changes in cerebral artery (CA) contractile responses secondary to altered alpha1-adrenergic-receptor (1-AR) subtype and/or specific protein kinase C isoform (PKC)-mediated downstream Ca2+-dependent and Ca2+-independent signal transduction pathways. An associated hypothesis is that development significantly alters 1-AR-subtype- and specific PKC isozyme-mediated expression of proto-oncogenes and genes representing vascular smooth muscle synthetic and/or proliferative phenotypes, as compared to adult contractile phenotype. Four Specific Aims are as follows. 1) What is the role of specific 1-AR subtypes and downstream effector proteins in signal transduction? 2) What is the role of specific PKC isoforms, extracellular signal regulated kinases (ERKs), Rho A/Rho kinases, and related kinases in signal transduction? 3) What is the role of specific 1-AR subtypes and PKC isoforms in gene regulation of developing vascular phenotypes? 4) What is the role of other signal transduction proteins presently poorly described in these signal transduction and gene regulation pathways? In ovine fetal, newborn, and adult CA, we will perform agonist-induced contractility and intracellular [Ca2+] measurements, Western immunoblots, RT- PCR, confocal microscopy, flow cytometry, 2D-gel-mass spectroscopy, gene silencing by double stranded RNA or morpholinos, gene upregulation, gene microarray/pathway analysis, and gene/protein discovery. Scientifically, the studies will advance our understanding of basic mechanisms whereby cerebral vessels change phenotypically and functionally with development from fetus, to newborn, to adult. Clinically, the studies relate to understanding the basis of the regulation of cerebral vascular tone, pressure, and blood flow in the fetus and/or premature newborn infant, and its dysregulation that results in intracerebral hemorrhage and serious neurologic sequelae.